Effects of acute and chronic starvation on central and peripheral noradrenaline turnover, blood pressure and heart rate in the rat

When faced with stress, an organism calls upon several mechanisms to mainta in biological homeostasis. The cardiovascular system is the first to respon d usually with an increase in arterial pressure and tachycardia. Therefore we investigated the central and peripheral sympathetic responses to acute a nd chronic starvation in Wistar rats. The noradrenaline (NA) turnover rate was determined in different catecholaminergic nuclei (A1, A2, A5, A6) as we ll as the arterial blood pressure and heart rate modifications. During acut e starvation (3 days of starvation), the NA turnover was increased in the A l and rostral A2 nuclei as well as in ventricles and kidneys and decreased in the A6 nucleus. During chronic starvation (4 consecutive cycles of 3 day s of starvation plus 1 day of feeding), the NA turnover was increased in th e A5 and caudal A2 nuclei as well as in ventricles and atria and decreased in the Al nucleus and kidneys. The arterial blood pressure revealed a gradu al decrease during the first 3 days of fasting but the heart rate was not m odified. We conclude that starvation should be considered as an unusual sta te of stress because of the absence of locus coeruleus response (A6 nucleus ) despite its well-defined role in stress reactions. One of the manifestati ons of these central and peripheral noradrenergic changes is the change in blood pressure during the starvation-feeding cycles.